A cyclic electric field has long been used for ion beam acceleration since the invention of linear RF accelerators and the cyclotron. In order to accelerate ions to an energy of several MeV, RF accelerators have been developed to repeatedly accelerate the ion beam, at a relatively low energy gain of approximately 100 KeV at each stage, in order to avoid difficulties in producing a mega-volt DC voltage. However, the RF accelerators still require generation of an RF voltage of approximately 100 KV peak voltage, which is achieved by the use of a high-Q resonance circuit for conversion of RF power (typically at low impedance of 50 ohms) into the high RF voltage.
At a low RF frequency (e.g., less than approximately 30 MHz), the resonant circuit is typically a lumped circuit comprising a coil and a capacitor (e.g., via distributed capacitance), rather than cavity resonators that are used at higher frequencies. For the application of RF accelerators used in ion implantation, the majority of ion species of interest are so-called heavy ions (e.g., Boron, Phosphorus and Arsenic), and because of their heavy masses, the velocity tends to be slow. On the cyclic acceleration induced by RF, the slow velocity translates into the use of low frequency RF voltage (e.g., less than 30 MHz), which is generated by a lumped resonance circuit (e.g., a resonator).